1. Field of the Invention
This invention relates to mass spectrometry. More particularly this invention relates to secondary neutral-particle mass spectrometry.
2. Description of the Invention
In the known procedures concerned with the secondary neutral-particle mass spectrometry, SNMS, neutral atoms and molecules are released from the surface of a solid body by ion bombardment, are ionized by the electron components of a low-pressure gas-discharge plasma and are then analyzed by a mass spectrometer. In an especially advantageous design of SNMS, ions from the ionizing plasma are accelerated in accordance with the direct bombardment technique toward the specimen by which method, in conjunction with an extremely planar adjustment of the equal potential planes in the ion acceleration path between plasma and specimen, a laterally highly homogeneous ion bombardment of the specimen surface can be achieved. If by lowering the voltage between the specimen and a reference electrode in the plasma, the ion energy is reduced to values around 100 eV any of the atomic mixing processes in the specimen typical for higher energies can almost completely be avoided. When employed for determining deep profiles of concentrations, this method, in conjunction with a laterally highly homogeneous ion removal, yields an extremely high depth resolution in the order of less than 1 nm.
These methods characteristic of the direct bombardment method of SNMS could, so far, be employed only on specimens whose electric conductivity was sufficiently high such that a dissipation of the imposed ion bombardment current could occur. It is the objective of the present invention to enable using this method also on completely or partially electrically non-conducive specimens.